Sealed micropump

ABSTRACT

A sealed micropump includes an integrated motor and at least one impeller for generating fluid flow inside a housing of the micropump. The impeller includes a radial sliding bearing with a spider bearing for supporting an impeller pin of the impeller inside the housing. The impeller pin includes a sheathing of a material different from a material of the spider bearing.

DESCRIPTION

The present invention relates to a sealed micropump comprising an integrated motor and at least one impeller for producing a fluid flow inside a housing of the micropump.

To provide cardiovascular support for patients having heart failure, systems are used that take over part of the pumping function or even all of the pumping function of the heart. In addition to systems that are seated on the outside of the heart, which are implanted invasively, systems are also known that are inserted minimally invasively as mechanical pumps, in particular into the left ventricle of the heart and the adjoining aorta. Continuous pumping pumps blood from the left ventricle into the aorta, so that enough oxygen-rich blood can circulate in the body of a heart failure patient. The US patent application US 2013/0303833 A1 , for example, describes an implantable blood pump, in which a blood flow is produced within the housing by a rotor disposed inside.

Because they are minimally invasively implanted, these systems have to be very small, in particular in terms of their radial circumference, for example having an outer diameter of no more 10 mm. These requirements for miniaturization of the components present a major challenge.

Based on this, the underlying object of the invention is to further improve the micropumps and systems known in the state of the art and achieve the highest possible efficiencies for delivering fluid or blood with high reliability and a long service life.

The invention proceeds from ideas of using blood pumps for minimally invasive implantation applications, which are based on the principle of a centrifugal pump with an integrated electric motor for the drive. The required blood flow is produced by means of an impeller. In such systems, the motor should be completely sealed. The torque can be transmitted without contact via a permanent-magnetic coupling (radial rotary coupling). To do this, it is usually necessary to support the impeller radially and axially. A so-called spider bearing comprising recesses or holes for the fluid flow can be provided on the housing side for radial support.

The invention provides a sealed micropump comprising an integrated motor and comprising at least one impeller for producing a fluid flow inside a housing of the micropump, whereby the pump comprises a radial sliding bearing with a spider bearing for supporting an impeller pin of the impeller of the pump inside the housing. The key element of the invention is that the impeller pin has a sheathing made of a material different from that of the spider bearing. The sheathing is fixedly connected to the impeller pin. This configuration allows tribologically advantageous material pairings to be realized for this sliding bearing and at the same time also enables space savings for the bearing arrangement of the impeller pin. In comparison with already known micropumps, said space saving can be used toward enlarging the recesses in the spider bearing surrounding the impeller pin. This has the significant advantage that it reduces pressure losses in this region.

The space required for the radial sliding bearing unavoidably represents a resistance to flow. The solution according to the invention makes it possible to enlarge the openings for the fluid flow in the spider bearing, because there is in particular no need for a bearing bushing inside the central opening of the spider bearing. The frictionally advantageous avoidance of a direct material pairing between the impeller pin and the spider bearing, which are usually both made of metallic materials, for example titanium, by means of an intermediate component made of a different material, in particular plastic, is realized by the sheathing of the impeller pin with such a different material which is provided according to the invention. Overall, this can minimize pressure losses at the radial sliding bearings, which increases the efficiency of the pump. Lower rotational speeds are furthermore possible during operation of the micropump, as a result of which there is less bearing wear overall and the fluid to be conveyed can also be conveyed more gently, so that, for example in the case of an intravascular blood pump, there is less damage to the delicate blood components. All in all, the configuration of the sealed micropump, and in particular the radial sliding bearing for the impeller provided within, enables a significantly reduced flow resistance for the fluid without undermining the reliability and service life of the micropump.

To produce the described sealed micropump, a metallic material is advantageously selected as the material for the impeller pin and for the spider bearing wheel, and the sheathing of the impeller pin is made of a plastic. The impeller pin and the spider bearing can in particular be made of titanium. The sheathing of the impeller pin is preferably made of polyetheretherketone (PEEK).

In a particularly preferred configuration of the sealed micropump, the cross-section of the impeller pin tapers in the region of the sheathing. The available installation space for the spider bearing can thus be increased particularly advantageously. Tapering the impeller pin makes it possible to configure the sheathing of the impeller pin in the bearing region such that there is no increase in the radial cross-section with respect to the region of the impeller pin outside the bearing. The effect on the spider bearing is such that the space required for the bearing bushing provided in conventional solutions inside the spider bearing is entirely available, so that the spider bearing and therefore its passage openings for the fluid can be designed to be correspondingly larger.

In particularly preferred configurations, the sheathing of the impeller pin is formed by a sleeve or a coating, in particular made of plastic, preferably polyetheretherketone, which is firmly and in principle permanently connected to the impeller pin, e.g. by gluing or overmolding. A sleeve having a wall thickness between 0.2 and 0.3 mm, in particular 0.25 mm, is especially suitable. Thinner or thicker layer thicknesses are possible as well. The impeller and the sheathing can form an integral component, whereby the outer diameter of the tribologically loaded impeller pin can be coated. It is possible in principle for the inner diameter of the spider bearing to alternatively or additionally be coated as well.

In another particularly preferred configuration of the micropump, the sheathing of the impeller pin forms a cap which comprises an extension beyond the spider bearing. This extension preferably tapers in upstream direction, thus creating a very advantageous shape in terms of flow, which enables better flow control around the bearing by reducing regions of separation and decreasing the congestion region and thereby contributes to reducing pressure losses and increasing the efficiency of the micropump. For the extension of the cap, conical or semi-ellipsoidal shapes in particular can be preferred.

The sealed micropump can particularly advantageously be a 30 blood pump, in particular an intravascular blood pump for microinvasive applications. The micropump can be a component of a ventricular cardiac support system, for example. The improvements of the micropump proposed here are particularly effective in systems with very small installation space, so that the advantages of the micropumps described here for intravascular blood pumps are an important factor. The outer diameter of the sealed micropump described here is preferably 10 mm or less, so that the requirements for blood pumps to be implanted in a minimally invasive manner are fully taken into account.

Further features and advantages of the invention emerge from the following description of design examples in conjunction with the drawings. The individual features can be realized individually or in combination with one another.

The drawings show:

FIG. 1 a current development of a sealed micropump comprising an integrated motor (partial section in longitudinal section) as the starting point of the invention;

FIG. 2 a longitudinal section through a radial sliding bearing of an impeller pin of the sealed micropump of FIG. 1;

FIG. 3 a longitudinal section through a radial sliding bearing of an impeller pin of a sealed micropump in a preferred embodiment of the invention and

FIG. 4 comparative cross-sections through the radial sliding bearings of FIG. 2 (4A) and the embodiment of a sliding bearing according to the invention of FIG. 3 (4B).

FIG. 1 shows the hydraulically active part of a completely sealed micropump 10 according to a current development of such pumps in cross-section. This micropump 10 is in particular intended to be a blood pump for minimally invasive implantations (intravascular blood pump). The micropump 10 is driven by an integrated electric motor, of which the motor shaft 11 is shown here. The rotor or the impeller 19 with the impeller blades (blades) 12 is radially and axially supported via a pivot bearing 13, whereby the torque is transmitted via a permanent-magnetic coupling 14. The required blood flow is produced inside the housing 15 of the sealed blood pump 10 by means of the impeller 19. In a sense, the impeller 19 forms a propeller (impeller) enclosed by a housing. The arrow 20 indicates the magnetically acting forces. The arrow 21 indicates the hydraulically effective forces. The impeller pin 190 (bearing pin) of the impeller 19 is additionally supported via a radial sliding bearing 16 which is located upstream. The radial sliding bearing 16 comprises a spider bearing 17 with a bearing bushing 18 inserted therein and the impeller pin 190 which rotates inside the bearing bushing 18. The bearing bushing 18 is provided to avoid a frictionally unfavorable material pairing between the impeller pin 190 and the spider bearing 17, for example the titanium-titanium material pairing, which is associated with a high degree of wear. The bearing bushing 18 can be made of polyetheretherketone (PEEK), so that the tribologically advantageous PEEK-titanium material pairing is present between the bearing bushing 18 and the impeller pin 190, which is very low friction and wear-resistant.

The blood flow inside the housing 15 is produced by the rotation of the impeller 19. The spider bearing 17 comprises a plurality of inlet openings for the blood. There are nonetheless pressure losses in the region of the spider bearing, because the spider bearing 17 constricts the cross-section thus creating a bottleneck. In the region of the base of the impeller 19, there are openings 22 in the housing 15 of the micropump 10, through which the fluid to be moved, in particular the blood, flows out.

FIG. 2 shows the region of the sliding bearing 16 for the radial support of the impeller pin 190 of the impeller 19 with the impeller blades 12 as a component of a micropump 10 according to FIG. 1 in a schematic longitudinal section. The impeller pin 190 is rotatably mounted inside the bearing bushing 18, whereby a narrow bearing gap 31 is provided between the impeller pin 190 and the bearing bushing 18. The bearing bushing 18 is located inside the spider bearing 17. The regions 32 indicate the openings of the spider bearing 17 through which the fluid, in particular the blood, can flow.

FIG. 3, on the other hand, shows a preferred embodiment of a sealed micropump 100 according to the invention, whereby this figure also shows the region of the sliding bearing 116. The section of the sealed micropump 100 according to the invention shown here shows the impeller pin 1190 of the impeller 119 with the impeller blades 112, whereby the impeller pin 1190 is rotatably mounted in the sliding bearing 116. Inside the housing 150 of the micropump 100, the spider bearing 117 is located in the region of the radial sliding bearing 116. In the region of the sliding bearing 116, the impeller pin 1190 is tapered. The tapering 1190 is surrounded by a sheathing 118. This sheathing 118 is made of a material different from that of the spider bearing 117. The sheathing 118 can in particular be made of PEEK and the spider bearing 117 can be made of a metallic material, in particular titanium.

Between the sheathing 118 and the spider bearing 117, there is a narrow bearing gap 131. The impeller pin 1190 sheathed with PEEK therefore rotates in the central recess of the spider bearing 117, thus realizing the tribologically advantageous material pairing of PEEK and titanium, for example. In comparison with a sliding bearing of FIG. 2, in the solution according to the invention the bearing bushing 18 is, in a sense, replaced by the sheathing 118, whereby the overall diameter remains unchanged. As a result of this measure, the space required by the bearing bushing 18 can be used for other purposes, and the openings 132 inside the spider bearing 117, which are provided for the fluid flow, can even be enlarged. Thus, with the same functional bearing dimensions (e.g. bearing diameter 1 mm, bearing gap 10 μm and wall thickness of the sheathing 0.25 mm), there is more cross-section available for the flow.

The sheathing 118 can particularly preferably also be implemented in the form of a cap 1180 which extends the sheathing 118 upstream and, as a result of being suitably shaped, provides advantages in terms of flow. The shape of the cap 1180 can in particular have a diameter that decreases upstream, in particular in a conical or semi-ellipsoidal shape. Improved flow control around the bearing 116 can thus be realized, as a result of which pressure losses are additionally reduced and the efficiency of the micropump 100 is increased.

FIG. 4 illustrates the configuration of the micropump 100 according to the invention in the region of the sliding bearing (Sub-figure 4B) in comparison to the sliding bearing of a micropump 10 of FIG. 1 (Sub-figure 4A) in cross-section. The illustration in Sub-figure A shows the sliding bearing with the impeller pin 19, which is rotatably mounted inside the bearing bushing 18, separated by the bearing gap 31. The bearing bushing 18 is located inside the spider bearing 17, which is secured inside the housing 15 of the micropump 10 via the spider bearing struts 170. The space 32 through which the fluid can flow is located between the individual spider bearing struts 170. In comparison with the configuration according to the invention in Sub-figure B, it becomes clear that the corresponding region 132 is significantly enlarged in the solution according to the invention. Sub-figure B shows the tapered region of the impeller pin 1190, which is directly surrounded by the sheathing 118 made of a different material. The narrow bearing gap 131 is located between the sheathing 118 and the interior of the spider bearing 117 (central recess of the spider bearing 17). The interior of the spider bearing 117 is connected to the housing 115 of the micropump 100 via the spider bearing struts 1170. This configuration makes it possible to enlarge the region 132 for fluid flow substantially in comparison to the sliding bearings according to FIG. 1. The micropump 100 according to the invention therefore produces significantly less pressure loss in the upstream region of the radial sliding bearing of the impeller pin.

Such a micropump can be used particularly advantageously as a blood pump for a cardiac support system, for example. 

1-12. (canceled)
 13. A cardiac support system comprising: a sealed micropump, the sealed micropump comprising: an integrated motor; and at least one impeller for generating fluid flow inside a housing of the micropump, wherein the at least one impeller comprises a radial sliding bearing comprising a spider bearing configured to support an impeller pin of the impeller inside the housing, and wherein the impeller pin comprises a sheathing comprised of a material different from a material of the spider bearing.
 14. The system of claim 13, wherein the impeller pin and the spider bearing each comprise a metallic material, and wherein the sheathing of the impeller pin comprises a plastic material.
 15. The system of claim 13, wherein the impeller pin and the spider bearing each comprise titanium, and wherein the sheathing of the impeller pin comprises polyetheretherketone (PEEK).
 16. The system of claim 13, wherein the impeller pin tapers in a region of the sheathing.
 17. The system of claim 16, wherein a radial cross-section of the sheathing of the impeller pin in a bearing region is the same as a radial cross-section of the impeller pin outside the bearing region.
 18. The system of claim 13, wherein the sheathing of the impeller pin comprises a coating.
 19. The system of claim 13, wherein the sheathing of the impeller pin comprises a sleeve.
 20. The system of claim 13, wherein the sheathing of the impeller pin extends beyond the spider bearing.
 21. The system of claim 20, wherein the sheathing comprises a cap, the cap comprising an extension extending beyond the spider bearing.
 22. The system of claim 21, wherein the extension tapers.
 23. The system of claim 21, wherein the extension is conical or semi-ellipsoidal.
 24. The system of claim 13, wherein the sealed micropump is configured to pump blood.
 25. The system of claim 13, wherein an outer diameter of the sealed micropump is at most 10 mm. 